1. Field of the Invention
The present invention relates to high performance electromechanical actuators, and, more particularly to a piezoelectric actuation/transduction system.
2. Description of Related Art
Many civilian and military applications require high performance electromechanical actuators. These include active vibration control, dynamic flow control in aerospace, underwater navigation and surveillance, and microphones, etc. High displacement and electromechanical output power are two main demands for actuators needed in many applications. In the past few decades, a great deal of effort has been devoted to two research fields: 1) the development of electromechanically active materials offering the desired properties and 2) the development of electromechanical devices which utilize the materials in an efficient manner. Since metal-ceramic composite actuators were invented (the so called Moonies), many device configurations have been exploited for amplified displacement and enhanced efficiency.
Recently, a hybrid actuation system (HYBAS) was developed to utilize the characteristics of the electromechanical performance of these two types of electroactive materials in a cooperative and effective way. This system is described in issued U.S. Pat. No. 7,394,181, July 2008 “Hybrid Electromechanical Actuator and Actuation System,” incorporated herein by reference. The system showed significantly-enhanced electromechanical performance compared to the performance of devices made of each constituent material individually. A theoretical model for the HYBAS was also developed, considering the elastic and electromechanical properties of the materials utilized in the system and the device configuration. A comparison was made with experimental data which showed that the model predicts the response of the HYBAS with good accuracy. More recently, new synthetic jet actuator concepts were invented copending patent application Ser. Nos. 60/842,458, 60/842,459, and 60/842,686), piezoelectric hybrid energy harvesting transducer (HYBERT) (issued U.S. Pat. No. 7,446,459, November 2008), incorporated herein by reference, and piezoelectric triple hybrid actuation system (TriHYBAS) based on the understanding of the electromechanical properties of piezoelectric materials and their applications.
In order to enhance the mechanical energy output to obtain high displacement, large mechanical load capability (high blocking force) with low applied voltage for a HYBAS, a full piezoelectric multilayer stacked hybrid actuation/transduction system (Stacked-HYBATS) was desired.
A novel full piezoelectric multilayer stacked hybrid actuation/transduction system has been developed. The system demonstrates significantly-enhanced electromechanical performance by utilizing the cooperative contributions of the electromechanical responses of multilayer stacked negative and positive strain components. Both experimental and theoretical studies indicate that, for this system, the displacement is over three times that of a same-sized conventional flextensional actuator/transducer. The coupled resonance mode between positive and negative strain components of the system is much stronger than the resonance of a single element actuation only when the effective lengths of the two kinds of elements match. Compared with a prior hybrid actuation system, the multilayer system is designed to provide high mechanical load capability, low voltage driving, and a high effective piezoelectric constant. The present system provides extremely high effective piezoelectric constants both at resonance and off-resonance frequencies. The effective piezoelectric constant can be altered by varying the size of each component: the degree of the pre-curvature of the positive strain components, the thickness of each layer in the multilayer stacks, and the piezoelectric constant of the material used. Since all the elements are piezoelectric components, the system can serve as projector and receiver for underwater detection. The performance of the system can be enhanced by improving the piezoelectric properties. With the present system, future actuator/transducer designs and piezoelectric material applications will reach a new level. The experimental results indicate that the stacked hybrid actuation/transduction system can provide displacement over three times larger than a same-sized conventional flextensional actuator/transducer with compatible mechanical load capability. Moreover, the coupled resonance between positive strain and negative strain components of a stacked hybrid actuation/transduction system is much stronger than the resonance peak of a single element actuation when the effective lengths of the two kinds of elements match each other.
An object of the present invention is to provide a piezoelectric multilayer stacked hybrid actuation/transduction system.
An object of the present invention is to provide a piezoelectric multilayer stacked hybrid actuation/transduction system which provides increased displacement over similar sized flextensional actuator/transducers with the same level of mechanical load capability.
Another object of the present invention is to provide a piezoelectric multilayer stacked hybrid actuation/transduction system which includes positive and negative strain components.
Yet another object of the present invention is to provide a piezoelectric multilayer stacked hybrid actuation/transduction system which provides an extremely high effective piezoelectric constant at resonance frequency and off-resonance frequencies.
Finally, it is an object of the present invention to accomplish the foregoing objectives in a simple and cost effective manner.